1. Field of the Invention
This invention relates generally to drilling and completing wellbores and more particularly to the use of vibratory and resonance devices downhole for performing selected drilling and completion operations for the production of hydrocarbons from subsurface formations.
2. Background of the Art
To obtain hydrocarbons such as oil and gas, boreholes or wellbores are drilled from surface locations into hydrocarbon-bearing subterranean geological strata or formations. A large amount of current drilling activity involves the drilling of highly deviated or substantially horizontal wellbores. Often, during the drilling of a wellbore, the drill bit and/or the drill pipe or tubing utilized for drilling the wellbore get stuck downhole, frequently at great distances from the wellbore mouth at the surface location. Additionally, during the completion, production and workover of the wellbores, various devices get stuck that must be retrieved from the wellbore. In many cases the stuck object must be freed and retrieved to continue to drill the wellbore or to continue to perform other operations. In many cases it is more desirable and less expensive to free (dislodge) the stuck object and either continue drilling of the wellbore or retrieve the object to the surface for repair or for substituting such object with a more suitable device than to leave the stuck object downhole. The object to be dislodged and/or retrieved is referred to in the industry as the "fish" and the process of dislodging and/or retrieving is referred to as "fishing."
A variety of fishing tools are utilized to free and retrieve stuck objects in wellbores in the oil and gas industry. A majority of these fishing tools are mechanical devices and do not include any local or downhole intelligence. Fishing tools utilizing resonance have been used for freeing stuck drill pipes and other objects in the wellbores. U.S. Pat. No., 4,815,328, issued to Albert Bodine and assigned to the assignee of the present invention and which is incorporated herein by reference, discloses a roller-type orbiting mass oscillator for generating resonance downhole. To loosen a drill pipe stuck in a wellbore, the device is attached at a suitable place to a drill pipe and is vibrated laterally by passing a pressurized fluid therethrough. The vibration rate is controlled by controlling the fluid flow at the surface. Such a device does not provide any positive method to determine when the stuck pipe has achieved resonance, nor any method for sweeping the operating frequency range to determine the optimum operating frequency, nor method to automatically adjust operating parameters such as the fluid flow rate to at continually or least periodically operate the tool at the optimum frequency.
More recently, surface-operated and surface-controlled resonance tools have been utilized to free stuck tubulars downhole. One such surface tool is available from Baker Hughes Incorporated referred to as the Resonance Tool, Product No. 140-52. It is known that all tubulars exhibit resonant frequencies that are a function of the free length of the tubular. This resonant tool is placed at the surface (near the wellhead). It applies acoustic energy to the stuck point through a work string in order to free the tubular. This tool contains an oscillator, a hydraulic power pack and a control panel. The control panel allows for remote control operations of the resonator. Such a tool requires a great amount of power, is large in size and heavy (several thousand pounds), is relatively inefficient because of its great distance from the stuck point and is expensive to manufacture.
To make a wellbore ready for production of hydrocarbons (i.e., to complete the wellbore), a liner (which is essentially a tubular string) is inserted into the wellbore with its upper end attached to the casing (previously installed in the uphole section of the wellbore) with a device known as a liner hanger. Cement is pumped downhole to fill the space (annulus) between the liner and the wellbore. Frequently the liner is moved up and down and/or rotated during cementing operations to fill any voids or channels in the annulus and to generally improve the integrity of the cement bond between the liner and the wellbore. Even using this method, the cement in the annulus in many wellbores includes voids and channels and is not packed as desired. It is therefore, desirable to have additional and/or alternative methods to improve the integrity of the cement in the annulus.
The present invention addresses the above-noted and other deficiencies of the prior art resonance devices and provides fishing tools with a downhole resonator, wherein the response of the stuck object to the resonator-induced pulses of mechanical energy is detected by a sensor associated with the fishing tool. A resonance tool also is provided to aid in the installation of liners and other cementing operations downhole. A control unit placed at the surface or in the resonance tool determines the optimum operating frequency within a range of frequencies and operates the resonator at such determined frequency. The invention further provides different configurations of the fishing tool for different applications. Additionally, this invention provides certain devices for securing the fishing tool to drill pipes at suitable locations above the stuck point. The fishing tools of the present invention may induce both the lateral and axial vibrations into the stuck object. The present invention also provides novel devices for latching the resonance tools to tubular members.